Lignin-empowered self-healing biomass ionogels for multi-modal flexible sensing

Sustainable and green materials are demanded for flexible electronics while the conventional hydrogel and organogel systems face dual challenges of environmental vulnerability such as dehydration and liquid leakage and limited multifunctionality. Here, a biomass-based ionogel with covalent-physical dual crosslinking networks by integrating lignin, poly(thioctic acid) (PTA), and a halometallate ionic liquid is reported. The optimized ionogel presents exceptional mechanical properties (75 kPa strength, 1230% elongation at break) and near infrared (NIR)-accelerated self-healing function benefiting from lignin's photothermal properties. Enabled by a decent conductivity (0.026 S/m), the ionogel manifest multi-stimuli sensing abilities, including strain, heat, and NIR light through distinct electrical signals including resistance and current changes. As a versatile multi-modal flexible sensor, it demonstrates robust human motion monitoring and accurate stimulus recognition of combined stimuli. This work advances high-value utilization of lignin and provides a green and practical strategy for fabricating multifunctional flexible sensors.